An optical scanner is used to generate machine-readable data which is representative of a scanned object such as a document or photograph. This is typically accomplished by employing a controlled light source located within the base of the scanner. The light source is reflected off the surface of a document and back onto an array of photosensitive devices which convert the light intensity into an electronic signal. Other scanner configurations include transmitting the light source through a transparent document, and then onto the array of photosensitive devices. The intensity of the light source is controlled, via a closed loop or an open loop, by utilizing calibration circuitry located within the scanner base.
Optical scanners and various components used within such scanners are disclosed in U.S. Pat. No. 4,926,041 for OPTICAL SCANNER of David W. Boyd; U.S. Pat. No. 4,937,682 for METHOD AND APPARATUS FOR PROVIDING CONTRAST/INTENSITY CONTROL IN A DOCUMENT SCANNER of Dan L. Dalton; U.S. Pat. No. 5,019,703 for OPTICAL SCANNER WITH MIRROR MOUNTED OCCLUDING APERTURE OR FILTER of David W. Boyd and John S. Deutschbein; and U.S. Pat. No. 5,038,028 for OPTICAL SCANNER APERTURE AND LIGHT SOURCE ASSEMBLY of David W. Boyd and C. William Elder, Jr.